Package On Package Memory Interface and Configuration With Error Code Correction

ABSTRACT

Information communication circuitry, including a first integrated circuit for coupling to a second integrated circuit in a package on package configuration. The first integrated circuit comprises processing circuitry for communicating information bits, and the information bits comprise data bits and error correction bits, where the error correction bits are for indicating whether data bits are received correctly. The second integrated circuit comprises a memory for receiving and storing at least some of the information bits. The information communication circuitry also includes interfacing circuitry for selectively communicating, along a number of conductors, between the package on package configuration. In a first instance, the interfacing circuitry selectively communicates only data bits along the number of conductors. In a second instance, the interfacing circuitry selectively communicates data bits along a first set of the number of conductors and error correction bits along a second set of the number of conductors.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of and claims priority to U.S. patent application Ser. No. 14/587,878, filed on Dec. 31, 2014, which claims priority to, the benefit of the filing date of, and hereby incorporates herein by reference, India Provisional Patent Application 583/CHE/2014, entitled “ENSURING DATA INTEGRITY FOR POP MEMORY USAGE IN FUNCTIONAL SAFETY CRITICAL APPLICATIONS WITH ASIL COMPLIANCE NEEDS,” and filed Feb. 7, 2014.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

The preferred embodiments relate to circuits with package on package (PoP) memory interfaces, as well as configurations including the PoP memory interface and coupled memory.

By way of background, FIG. 1 illustrates a cross-sectional side view of an integrated circuit PoP designated generally at 10. The configuration as shown in FIG. 1 is consistent with the prior art, but notably the preferred embodiments also are suitable for implementing in a same configuration, albeit with greater functionality and benefits as detailed later. By way of general introduction to both the prior art and the related packaging considerations of the preferred embodiments, therefore, PoP 10 has two or more integrated circuit packages 20 and 30 (also known as chips) stacked relative to one another, typically for saving space to serve application requirements where area or volume is constrained. For example, automobile applications in confined areas of a vehicle may call for PoP devices, as may other consumer devices, such as cell phones and cameras. In general, the overall dimensions of integrated circuit PoP, shown generally two dimensionally D1 by D2, but understood to include a third dimension D3 perpendicular to D1 and D2, typically occupy one cubic inch, or less.

Each device 20 and 30 includes at least one functional die 22 and 32, respectively, atop a respective substrate 24 and 34. The two (or more) stacked PoP devices 20 and 30 may serve comparable functions such as multiple memories, or in a mixed logic-memory stacking the devices may differ, such as having a System-On-A-Chip (SoC) processor as the lower device, with memory stacked on top of the SoC processor and providing electronic storage to the processor. Each functional die 22 and 32 is encapsulated in a respective cover 26 and 36. Each package 20 and 30 has a respective set of connectors, typically by way of a ball grid array (BGA) 28 and 38. BGA 28 allows electrical connections between packages 20 and 30, while BGA 38 allows connections between package 30 and additional lines, such as are typically on a printed circuit board (PCB). In any event, the stacked arrangement of the PoP configuration reduces the two-dimensional space needed as compared to arranging the two chips separately in a generally same two dimensional plane. Other PoP advantages include shorter track length in the connections between the stacked devices, thereby improving performance, such as increasing speed and noise resistance.

While PoP configurations are increasingly useful and provide benefits as described above, it has been observed in connection with the preferred embodiments that PoP configurations may provide limitations. Specifically, because of the confined volume created by PoP stacking, typically the number of pin connections between the stacked devices is limited, due to the layout of die on each stacked device and the stacked perimeter, as typically occupied by the BGA. One manner observed in which such pin limitations arises is the lack of support for data checking by memories manufactured for PoP applications. More particularly, as technology advances, there again arises a need for smaller devices where PoP might appear usable, but at the same time some environments and applications also are increasing the use of so-called “mission critical” data. For example, in contemporary automotive applications, data that formerly was not mission critical is evolving toward mission critical, as may be guided by manufacturer requirements or regulations, such as via Automotive Safety Integrity Level (ASIL). Consider the instance of video data for a vehicle backup camera; such data in some applications may not by itself be mission critical when used solely to depict an image to a vehicle operator, but as such data becomes used for vehicle control, such as controlling brakes, steering, or acceleration, the criticality of the data is considerably increased. Such mission critical data, by definition, requires assurances of greater if not absolute accuracy. In PCB layouts, some accuracy is sometimes achieved through the use of a single parity bit per byte (or other quantum) of data, or for greater accuracy, error code correction (ECC) bits are used, wherein multiple ECC bits are generated, typically by hashing a byte (or other quantum) of data. Either the parity bit or ECC bits are used to verify data that is simultaneously communicated with the parity/ECC, and in the instance of an error then correction of the error is facilitated. For PoP applications, however, memory manufacturers construct memories (e.g., low power double data rate memory—LPDDR2/3) with a limited number of pins, presumably due to the confined area of PoP technology. As a result, such memory does not support parity/ECC. Moreover, the prior art PoP memory interface also does not support parity/ECC, again presumably due to the space constraints of PoP stacking as well as the general availability of memory usable in PoP architectures.

Further with respect to the above, FIGS. 2a and 2b illustrate electrical block diagrams of the limitations in prior art PoP LPDDR2 memory and interfacing configurations. For example, FIG. 2a illustrates a 32-bit PoP external memory interface PEMIF₁ which, consistent with the typical commercially available 32-bit PoP memory PMEM₁ (e.g., SDRAM), provides only data pins D[31:0], but no additional error information. Similarly, FIG. 2b illustrates a 16-bit PoP external memory interface PEMIF₂ which, consistent with the typical commercially available 16-bit PoP memory PMEM₂, provides only data pins D[15:0] but no additional error information.

Given the preceding, the present inventors have identified potential improvements to the prior art, as are further detailed below.

BRIEF SUMMARY OF THE INVENTION

A preferred embodiment provides information communication circuitry, including a first integrated circuit for coupling to a second integrated circuit in a package on package configuration. The first integrated circuit comprises processing circuitry for communicating information bits, and the information bits comprise data bits and error correction bits, where the error correction bits are for indicating whether data bits are received correctly. The second integrated circuit comprises a memory for receiving and storing at least some of the information bits. The information communication circuitry also includes interfacing circuitry for selectively communicating, along a number of conductors, between the package on package configuration. In a first instance, the interfacing circuitry selectively communicates only data bits along the number of conductors. In a second instance, the interfacing circuitry selectively communicates data bits along a first set of the number of conductors and error correction bits along a second set of the number of conductors.

Numerous other inventive aspects and preferred embodiments are also disclosed and claimed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 illustrates a cross-sectional side view of a prior art integrated circuit package on package (PoP) configuration.

FIG. 2a illustrates a prior art 32-bit PoP external memory interface

FIG. 2b illustrates a prior art 16-bit PoP external memory interface.

FIG. 3 illustrates a combined block and schematic view of an external memory interface in accordance with a preferred embodiment.

FIG. 4 illustrates a combined block and schematic view of a configuration including interface EMIF₂ of FIG. 3, when connected to a memory MEM for supporting 16-bit critical DATA in a PoP configuration.

FIG. 5 illustrates a combined block and schematic view of a configuration including interface EMIF₂ of FIG. 3 when connected to a memory MEM for supporting 32-bit non-critical DATA in a PoP configuration.

FIG. 6 illustrates a memory address space for demonstrating an additional preferred embodiment aspect in connection with dynamic switching to accommodate both critical and non-critical DATA.

FIG. 7 illustrates an electrical block diagram of interface EMIF₂ in a non-PoP configuration supporting 32-bit DATA with ECC, and using two 16-bit memories MEM_(16.1) and MEM_(16.2), and a third 16-bit (or 8-bit) memory MEM_(16.3) for ECC.

FIG. 8 illustrates an electrical block diagram of interface EMIF₂ in another non-PoP (e.g., PCB) configuration, which in FIG. 8 again supports 32-bit DATA with ECC, but here using a single 32-bit memory MEM₃₂ for DATA, along with again a 16-bit (or 8-bit) memory MEM_(16.3) for ECC.

FIG. 9 illustrates an electrical block diagram of interface EMIF₂ in a non-PoP (e.g., PCB) configuration that supports 16-bit DATA with ECC, and using a single 16-bit memory MEM_(16.1) for DATA and a single 16-bit (or 8-bit) memory MEM_(16.3) for ECC.

DETAILED DESCRIPTION OF EMBODIMENTS

FIGS. 1, 2 a, and 2 b were discussed above in the Background Of The Invention section of this document, and the reader is assumed to be familiar with that discussion.

FIG. 3 illustrates a combined block and schematic view of an external memory interface EMIF₂ in accordance with a preferred embodiment. Interface EMIF₂ communicates information, including DATA and ECC for that DATA, to a memory, the latter of which is shown in later Figures. Interface EMIF₂ may be part of a larger memory interface with physical connectors (e.g., having one or more pins) beyond those shown and discussed below. For example, interface EMIF₂ may be part of a circuit, such as a processor, including a microprocessor or digital signal processor, that includes other connectors as understood by one skilled in the art. Such other connectors, however, are neither shown nor discussed so as to simplify the document. In any event and as detailed in this document, interface EMIF₂ overcomes limitations of the prior art in that it facilitates a combined PoP structure, as between interface EMIF₂ and standard prior art memories, that supports error checking such as ECC. In addition, interface EMIF₂ also may be used in non-PoP configurations, for example with one or more memories located on a PCB.

In a preferred embodiment, interface EMIF₂ includes a number of physical connectors PHYx, where each such connector PHYx represents a number of bits/pins/conductors for interfacing with an external memory circuit or chip, such as various types of SDRAM including LPDDR2/3 memory chips. For sake of example, each physical connector PHYx provides 8 bits (i.e., a byte) of information, although other sized data quantities could be represented, including a single connector/pin per bit. Nominally, interface EMIF₂ includes four such connectors for DATA, namely, DATA PHY0, DATA PHY1, DATA PHY2, and DATA PHY3, and one such connector for ECC, namely, ECC PHY_(ECC). In this sense, therefore, the external connectors of interface EMIF₂ appear the same as a prior art non-PoP (e.g., PCB) interface, operable to connect to a memory that supports four bytes of DATA and one byte of ECC, and indeed interface EMIF₂ also may serve such a role. As detailed below, however, interface EMIF₂ also may serve PoP configurations, preferably including a 16-bit PoP with ECC arrangement, or a 32-bit PoP without ECC arrangement.

Within interface EMIF₂ are shown an ECC bus and a DATA bus, and interface EMIF₂ further includes Processing Circuitry 40 coupled to each such bus, to illustrate that the device (e.g., processor), including or communicating via EMIF₂, permits Processing Circuitry 40 to process up to X bits of DATA (e.g., X=32) and Y bits of ECC (e.g., Y=8 or less). The lowest first and second DATA bytes B0 (i.e., D[7:0]) and B1 (i.e., D[15:8]) of the DATA bus are connected to respective physical connectors DATA PHY0 and DATA PHY1, and the fourth DATA byte B3 (i.e., D[31:24]) is connected to physical connector DATA PHY3. The third DATA byte B2 (i.e., D23:16), however, is connected as a first input to a multiplexer 42. The sole ECC byte ECC[7:0] (or other number of bits in a different preferred embodiment) is connected to both physical connector ECC PHY_(ECC) and the second input of multiplexer 42. The output of multiplexer 42 is connected to the physical connector DATA PHY2. The control input of multiplexer 42 is connected to the output of an AND gate 44, which for reasons detailed below has two input signals: (1) PoP_Narrow; and (2) ECC_en. In a preferred embodiment, these two input signals are internally generated (i.e., asserted or de-asserted), such as from register outputs, in response to software as may be run by Processing Circuitry 40 or the like, and consistent with the desired functionality described below.

FIG. 4 illustrates a combined block and schematic view of a configuration including interface EMIF₂ of FIG. 3, in a first instance, wherein interface EMIF₂ is connected to a memory MEM (e.g., 32-bit SDRAM) for supporting 16-bit critical data in a PoP configuration. By way of illustration, the PoP connectivity in general is shown by a dashed rectangle that includes interface EMIF₂ and memory MEM, as may be generally oriented physically in the manner shown and discussed above in FIG. 1. In FIG. 4, however, the preferred embodiment PoP configuration permits interface EMIF₂ to write, preferably at the same time, 16 DATA bits along with 8 bits of ECC, to memory MEM. At the outset, therefore, note that memory MEM is commercially available for PoP configurations, but such memory does not include dedicated ECC pins, presumably due to the space constraints of PoP considerations. In combination with the preferred embodiment interface EMIF₂, however, additional ECC protection is provided, as explored below.

In FIG. 4, the physical connectors from interface EMIF₂ of DATA PHY0 and DATA PHY1 of the first and second two DATA bytes B0 and B1, respectively, are connected to respective physical connectors on memory MEM. In addition, the physical connector from interface EMIF₂ of DATA PHY2, which recall is from the output of multiplexer 42, is connected to respective physical connector DATA PHY2 on memory MEM. Lastly, note that physical connector DATA PHY3 for the third byte on memory MEM is left open (i.e., disconnected from interface EMIF₂) so that, in the present configuration, any information at that interface constitutes “don't care” information.

The operation of the FIG. 4 configuration is now described. Because the configuration is intended to support PoP 16-bit with ECC, then the PoP_Narrow signal is asserted for the narrower option of 16 bits rather than 32 bits, and the ECC en signal is asserted for including ECC information. In response, the output of AND gate 44 is asserted to that multiplexer 42 selects the ECC[7:0] information and outputs it to the physical connectors DATA PHY2 of both interface EMIF₂ and memory MEM. As a result, during a write of DATA from interface EMIF₂ to memory MEM, memory MEM receives, as its D[15:0], 16 bits of DATA from the interface EMIF₂ DATA bus; at the same time, memory MEM receives, as its D[23:16], 8 bits of ECC from the interface EMIF₂ ECC bus. Note further that while the various Figures and descriptions herein address the writing from interface EMIF₂ to memory MEM, the same preferred embodiment contemplates the reading of memory MEM by interface EMIF₂, in which case multiplexer 42 would serve as a demultiplexer, and the arrow directions depicting information flow in the various Figures would be reversed. In either event, therefore, the FIG. 4 configuration supports ECC communication, even in the PoP environment.

FIG. 5 illustrates a combined block and schematic view of a configuration including interface EMIF₂ of FIG. 3 in a second instance, wherein interface EMIF₂ is connected to a memory MEM (e.g., 32-bit SDRAM) for supporting 32-bit non-critical data in a PoP configuration. Thus, the FIG. 5 PoP configuration permits interface EMIF₂ to simultaneously write (or read) 32 DATA bits, without ECC. Again, memory MEM is commercially available for PoP configurations. Also in FIG. 5, the physical connectors from interface EMIF₂ of all four data bytes, DATA PHY0, DATA PHY1, DATA PHY2, and DATA PHY3 are connected to respective physical connectors on memory MEM.

The operation of the FIG. 5 configuration is now described. Because the configuration is intended to support PoP 32-bit without ECC, then neither the PoP_Narrow signal nor the ECC_en signal is asserted. In response, the output of AND gate 44 is de-asserted, so that multiplexer 42 selects the D[23:16] of DATA and outputs it to the physical connectors DATA PHY2 of both interface EMIF₂ and memory MEM. As a result, during a write of DATA from interface EMIF₂ to memory MEM, memory MEM receives DATA from the EMIF₂ DATA bus at each of data inputs D[31:0]. In other words, fully 32 bits of DATA pass between interface EMIF₂ and memory MEM, without any ECC information. Thus, the same preferred embodiment interface EMIF₂ has been shown in FIGS. 4 and 5 to support PoP configurations, wherein one configuration (FIG. 4) supports ECC while another supports higher bandwidth (e.g., 32 bits versus 16 bits) without ECC.

FIG. 6 illustrates a memory address space 50 for demonstrating an additional preferred embodiment aspect in connection with dynamic switching of multiplexer 42 of FIG. 5, so as to accommodate both critical and non-critical DATA. Specifically, memory address space 50 is intended to illustrate a preferred mapping or storing of DATA within the address space addressable by interface EMIF₂, where as shown each region Rx of the space stores only critical or non-critical DATA but not a combination of the two. With this preferred embodiment partitioning of data storage, further in the preferred embodiment the FIG. 5 PoP configuration may achieve ECC protection in one instance for either the critical DATA regions R1 and R3, 16 bits at a time, or non-ECC protection in a different instance for any of the non-critical DATA regions R0, R2, and R4, 32 bits at a time. For example looking to region R0 which stores non-critical DATA, in the instance when interface EMIF₂ is communicating (e.g., writing) this non-critical DATA to memory MEM, then as indicated graphically in FIG. 6 to the right of that region, AND gate 44 is de-asserted, so that multiplexer 42 selects D[23:16] and outputs that byte B2 of DATA to the DATA PHY2 physical connectors of interface EMIF₂ and memory MEM; at the same time, interface EMIF₂ communicates the other three DATA bytes B0, B1, and B3 on respective connectors PHY0, PHY1, and PHY3. In this instance, therefore, 32 bits of non-critical DATA are communicated without ECC, but in a PoP configuration. To the contrary, however, and for example looking to region R1 which stores critical DATA, when interface EMIF₂ is communicating (e.g., writing) this critical DATA to memory MEM, then as indicated graphically in FIG. 6 to the right of that region, AND gate 44 is asserted, so that multiplexer 42 selects ECC[7:0] and outputs that information to the DATA PHY2 physical connectors of interface EMIF₂ and memory MEM; at the same time, interface EMIF₂ writes the lower two DATA bytes B0 and B1 (and B3 is a don't care). In this instance, therefore, 16 bits of critical DATA are communicated, along with ECC, in a PoP configuration. Thus, FIG. 6 further demonstrates that the FIG. 5 configuration supports dynamic switching so as to communicate either ECC or non-ECC protected DATA, in a PoP configuration.

FIG. 7 illustrates an electrical block diagram of interface EMIF₂ in a non-PoP (e.g., PCB) configuration that supports 32-bit DATA with ECC, using two 16-bit memories MEM_(16.1) and MEM_(16.2) for DATA, and a third 16-bit (or 8-bit) memory MEM_(16.3) for ECC. First, note that for sake of simplification, the internal schematic items of interface EMIF₂ shown and discussed above are eliminated from the Figure. Further in FIG. 7, the lower two DATA bytes from interface EMIF₂ are connected to communicate two bytes to 16-bit memory MEM_(16.1), and the upper two DATA bytes from interface EMIF₂ are connected to communicate two bytes to 16-bit memory MEM_(16.2). Further, the 8 bits from the physical connector ECC PHY_(ECC) of interface EMIF₂ are connected to 8 bits in third memory MEM_(16.3). Thus, in the earlier PoP configuration preferred embodiments wherein the physical connector ECC PHY_(ECC) of interface EMIF₂ is unused, in the FIG. 7 preferred embodiment that additional connector provides support for non-PoP configurations. The FIG. 7 preferred embodiment configuration, therefore, demonstrates that interface EMIF₂ also may be used to support 32 DATA bits plus ECC, preferably in a non-PoP configuration, because the number of memory chips involved is likely to exceed the constrains of PoP configurations.

FIG. 8 illustrates an electrical block diagram of interface EMIF₂ in another non-PoP (e.g., PCB) configuration, which in FIG. 8 again supports 32-bit DATA with ECC, but here using a single 32-bit memory MEM₃₂ for DATA, along with again a 16-bit (or 8-bit) memory MEM_(16.3) for ECC. In FIG. 8, therefore, each DATA byte from interface EMIF₂ is connected to a respective DATA byte position in memory MEM₃₂, that is, the first DATA byte from interface EMIF₂ connects to the first DATA byte in 32-bit memory MEM₃₂, the second DATA byte from interface EMIF₂ connects to the second DATA byte in 32-bit memory MEM₃₂, and so forth. Further, the 8 bits from the physical connector ECC PHY_(ECC) of interface EMIF₂ are connected to 8 bits in memory MEM₁₆₃. The FIG. 8 preferred embodiment configuration, therefore, demonstrates that interface EMIF₂ also may be used to support 32 DATA bits plus ECC using, for the DATA, a single DATA memory chip, as opposed to the two DATA memory chips in FIG. 7. Further, again the physical connector ECC PHY_(ECC) of interface EMIF₂, unused for PoP configurations, in FIG. 8 provides support for non-PoP configurations.

FIG. 9 illustrates an electrical block diagram of interface EMIF₂ in a non-PoP (e.g., PCB) configuration that supports 16-bit DATA with ECC, and using a single 16-bit memory MEM_(16.1) for DATA and a single 16-bit (or 8-bit) memory MEM_(16.3) for ECC. The FIG. 9 preferred embodiment configuration demonstrates that interface EMIF₂ also may be used to support 16 DATA bits plus ECC, preferably in a non-PoP configuration. Additionally, once more, FIG. 9 demonstrates that the physical connector ECC PHY_(ECC) of interface EMIF₂, unused for PoP configurations, provides support for non-PoP configurations.

From the above, various embodiments provide numerous improvements to the prior art. Such improvements include circuitry with an external memory interface that provides PoP memory configurations with available ECC support. Moreover, the preferred embodiments contemplate that a same interface can further support alternative functionality within a PoP configuration so that critical data has ECC support, while non-critical data does not, but the latter is afforded greater bandwidth (e.g., 32 bits) than the ECC supported data (e.g., 16 bits). Still further, the same preferred embodiment interface may support one or more non-PoP configurations. Moreover, various aspects have been described, and still others will be ascertainable by one skilled in the art from the present teachings. For example, while multiplexer 42 has been shown as included within the same integrated circuit that comprises Processing Circuitry 40, external glue logic may be used in an alternative embodiment. Thus, while various alternatives have been provided according to the disclosed embodiments, still others are contemplated. Given the preceding, therefore, one skilled in the art should further appreciate that while some embodiments have been described in detail, various substitutions, modifications or alterations can be made to the descriptions set forth above without departing from the inventive scope, as is defined by the following claims. 

1. Information communication circuitry, comprising: a first integrated circuit coupled to a second integrated circuit in a package on package configuration, the first integrated circuit comprising processing circuitry for communicating information bits, and wherein the information bits comprise data bits and error correction bits, the error correction bits indicate whether data bits are received correctly; the second integrated circuit comprises a memory for receiving and storing a portion of the information bits; and interfacing circuitry coupled to the first integrated circuit and second integrated circuit, and operable to: determine whether to access a first region of the memory; and when accessing the first region of the memory, selectively communicate data bits along a first set of the conductors between the first integrated circuit and the second integrated circuit and error correction bits along a second set of the conductors between the first integrated circuit and the second integrated circuit.
 2. The information communication circuitry of claim 1 wherein the number of conductors comprises 32 conductors and 16 data bits are communicated when accessing the first region of the memory.
 3. The information communication circuitry of claim 2 wherein in 8 error correction bits are communicated when accessing the first region of the memory.
 4. The information communication circuitry of claim 2 wherein in up to 8 error correction bits are communicated when accessing the first region of the memory.
 5. The information communication circuitry of claim 1 wherein the first region stores critical data.
 6. The information communication circuitry of claim 1 wherein the first integrated circuit is coupled to the memory.
 7. The information communication circuitry of claim 1 wherein the first integrated circuit is further for coupling to at least one additional integrated circuit, comprising a memory, in a non-package on package configuration.
 8. The information communication circuitry of claim 7: wherein the number of conductors provides a first set of conductors; wherein the interface circuitry comprises a second set of conductors; and wherein the interfacing circuitry is further for communicating data bits along the first set of conductors while concurrently communicating error correction bits along the second set of conductors.
 9. The information communication circuitry of claim 8: wherein the first set of conductors is 32 conductors; and wherein the second set of conductors is 8 conductors.
 10. The information communication circuitry of claim 8 wherein the first integrated circuit and coupled second integrated circuit together fit within a volume of one cubic inch or less.
 11. The information communication circuitry of claim 10: wherein the first set of conductors is 16 conductors; and wherein the second set of conductors is 8 conductors.
 12. The information communication circuitry of claim 1 and further comprising the second integrated circuit.
 13. The information communication circuitry of claim 1 wherein the interfacing circuitry comprises a set of conductors and a multiplexer wherein the conductors output data bits and the multiplexer outputs only error correction bits when accessing the first region of the memory.
 14. The information communication circuitry of claim 1 wherein the information bits comprise automotive video information bits.
 15. The method of claim 1 wherein up to 8 error correction bits are communicated when accessing the first region of memory in the second integrated circuit.
 16. A method of communicating information bits between a first integrated circuit and a second integrated circuit in a package on package configuration, the method comprising: receiving, by an interfacing circuitry, information bits from the first integrated circuit, the information bits comprising data bits and error correction bits, the error correction bits indicate whether data bits are received correctly; determining, by the interfacing circuitry, whether to access a first region of memory in the second integrated circuit; and when accessing the first region of memory in the second integrated circuit, selectively communicating, by the interfacing circuitry along conductors data bits along a first set of the conductors between the first integrated circuit and the second integrated circuit and error correction bits along a second set of the conductors between the first integrated circuit and the second integrated circuit.
 17. The method of claim 16 wherein the number of conductors comprises 32 conductors and 16 data bits are communicated when accessing the first region of memory in the second integrated circuit.
 18. The method of claim 16 wherein up to 8 error correction bits are communicated when accessing the first region of memory in the second integrated circuit. 